Preparation of a titania gel-boria catalyst



Patented July 20, 1948 PREPARATION OF A TITANIA .GEL-BORIA CATALYST Gerald G. Connolly, Elizabeth, N. J., assignor to Standard Oil Development Company, a corporation of Delaware.

No Drawing. 7 Application July 27, 1946, Serial'lNo. 686,729

4 Claims.

This application is a continuation-in-part of my copending application Serial No. 455,729, now U. 8. Patent No. 2,424,152 fiied August 22, 1942, which is in turn a division of my Serial No. 426,- 120, filed January 9,1942, now U. S. Patent No. 2,339,838, issued January 25, 1944.

The present invention relates to improved catalysts, particularly suitable for the catalytic treatment of hydrocarbon oils, and to methods for preparing the said catalysts. As is generally known, catalysts such as acid treated clays of the Montmorillonite type have been previously employed in the cracking of hydrocarbon oils, such as gas oil, to produce fractions boiling substantially within the gasoline range. These catalysts, as a rule, have given eminent satisfaction and when properly employed, a good yield of high octane number gasoline may [be obtained by cracking a suitable ga oil in vapor phase in the presence of such catalysts. 'As is generally known, however, the cracking of hydrocarbon oils in the presence of catalysts results in the deposition of carbonaceous materials upon the catalyst and in a stationary bed type of operation, that is to say, an operation in which the oil undergoing cracking is forced through a stationary bed of such catalyst, there comes a time when the operation must be discontinued to revivify and regenerate the catalyst. The most practical method for accomplishing the regeneration of the catalyst is to treat the catalyst with air or other free oxygen-containing gas at active combustion temperatures, say a temperature of about 700 F. to 1000 Foo-r thereabouts, whereupon the carbonaceous deposits are consumed .by combustion and catalyst is thereby restored substantially to its original activity.

'There are, however, certain limitations imposed on a process employing an acid treated clay, these limitations being with respect to the temperatures to which the catalyst may be exposed. For instance, ordinarily an acid treated claymay not be exposed to temperature conditions exceeding 1050 F. or 1100 F. without causing baking, fusion, or otherwise impairing the structure of the catalyst and thereby lowering its efiiciency. This fact embodies certain precautionary measures which must be employed particularly'during the regeneration of such a catalyst. For instance, ordinarily instead of using air during the regeneration, it is quite common to dilute the air with a more or less inert gas, such as flue gas, in order to prevent its rapid consumption of the carbonaceous deposits on the catalyst and with it temperature rises above the aforementioned limits, namely, 1100 F. so as to protect the catalyst during its regeneration. Obviously, it :would be desirable to regenerate a catalyst as rapidly as possible in a stationary bed type of operation in order to operate the process so that the catalyst is in the onstream operation for a greater total time during a given period; but, as previously stated, it is not possible to employ air ordinarily, because the high content of oxygen releases more '1 heat than can be withdrawn from the system rapidly, even though cumbersome and expensive cooling means are disposed within the mass of catalyst.

I have now discovered anew cracking catalyst which is very stable towardhigh degrees of heat. Essentially, this catalyst consists of a boron oxide supported on a titanium oxide gel. My tests have shownth-at this catalyst may be subjected to pe a es as high as 1840 F. without serious.- ly afiecting the activity of the catalyst. Thus, it is evident that this catalyst may be regenerated at much higher temperatures than have pre viously been considered suitable for the reactivation of cracking catalysts. Therefore, it is possible to regenerate using air or even an oxygenenriched air without impairing the structure or the activity of the catalyst. As mentioned hereinbefore, by regenerating at a high temperature the time required for regeneration is considerably shortened and as a result the catalyst may be used for the desired reaction for a larger proportion'of the cycle.

I shall now set forth several methods of pre-' paring my improved catalyst in the form of the succeeding specific examples. It will be understood that the precise details hereinaiter enu merated are purely illustrative and do not im pose anylimitation on the scope of my invention, for it will be obvious to those skilled in the art that reasonable modifications of the disclosed processes may be made without departing from the-spirit of my invention.

The dry titania gel may be impregnated with a solution of boric acid. It is preferred to use just the right amount of solution to moisten the catalyst without leaving any residual liquid. The concentration of boric acid in the solution is adjusted to give the desired proportion of boria in the finished catalyst. Because of the limited solubility of boric acid in water, it is usually preferred to use a hot solution to increase the solubility so that a sufficient amount may be introduced into the catalyst. However, where it is desired to produce a catalyst with a high proportion of boria, it may be necessary to use a series of impregnation operations and to dry the catalyst between each impregnation. In this manner any desired amount of boria may be introduced into the catalyst. The impregnated material is dried at a temperature of 200-300 F. and is then activated by heating for several hours at a temperature from about 600 to about 1000" F. If the catalyst is to be used in other than powder or granular form, it may be extruded, pilled or otherwise shaped prior to the drying operation. In 1 place of impregnating the dry gel with the boric acid solution, in some instances it may be desirable to impregnate the titania jelly with said solution or to mix the moist jelly with dry boric acid. Also, other compounds of boron besides boric acid which can be readily converted to boric oxide may be used to impregnate the titania gel. In general, these catalysts may be prepared by impregnating, mixing or otherwise incorporating boria or any compounds readily converted to boria with titania gel in any suitable stage of its formation.

As a more specific illustration of the operation of the invention, the following examples are given:

Example 1 Equal volumes of 1.2 normal ammonium hy droxide and 1.0 normal titanyl sulfate solutions are mixed with vigorous stirring to form a highly voluminous jelly of titania. The supernatant liquid has an excess alkalinity of about 0.01 to 0.10 normal. The jelly is allowed to stand overnight aiter which it is washed by deoantation until incipient peptization sets in. In the case of jellies formed in alkaline solution, one or two washings are usually all that can be tolerated before peptization begins. At this point the jelly is dried, preferably at a temperature above the boiling point of water. To avoid decrepitation, if the gel is desired in granular form, it is then further heated at a temperature of about 800 F. The dried gel is then further washed with water until substantially free of reaction products. This material when activated for three hours at 1000 F. with a particle size of 4-12 mesh will have an apparent density of between 1.00 and 0.80 grams per cubic centimeter.

Example 2 The same solutions used in Example 1 are mixed in such proportions that the supernatant liquid is acid, usually 0.001 to about 0.1 normal. The jelly is washed by decantation and it will be found in this case that it does not peptize so rapidly as the jelly formed in alkaline solutions. F

Usually five or more washings can be tolerated before peptization begins. The jelly is then dried, heated and rewashed as before. In this case the product will have an apparent density of about 1.0 to 1.3 grams per cubic centimeter.

, .I have found that the best titania gels on the acid side are formed from solutions between neutrality and about 0.005N excess acidity. Above apparently is impossible.

4 according to Patrick U. S. 1,682,242 was both impure and of too high apparent density. Also a titania gel made according to Klosky and Marzano, Titania Jellies, Journal of Physical Chemistry, volume 29, page 1125, had the same objections only to a greaterdegree. Patrick reacted a soluble titanate as sodium titanate and acid to an excess acidity of 0.1-0.5N and depended on washing the NazO and impurities from the jelly. Klosky and Marzano made their gel using an acid solution of sodium titanate and an alkali, the alkali being carried to about 2.0N excess. They attempted to wash the jelly alone which In both cases, Patrick, and Kl'osky and Marzano had in mind more the a use of their titania gels as adsorbents which could be reactivated at comparatively low temperatures.

With catalysts, particularly cracking catalysts, where carbon is formed in the reaction, it is another matter. Here the carbon is burned of! repeatedly at rather high temperatures around 1000 F. or so, and as stated above, the gel must be sufliciently pure and of sufficiently low apparent density to withstand repeated high tempera-- turev regenerations.

Example 3 A dry titania gel with a particle size of 4-12 mesh and having an apparent density of 0.96 gram per cubic centimeter was mixed with sufficient boric acid solution to moisten the gel and to incorporate therein 5% of borio oxide. The moist mass was pilled and activated at a temperature of 800 F. for 3 hours or more. These pills were then used for cracking an East Texas gas oil of 33.8 A. P. I. gravity for a two hour period at a feed rate of 0.6 volume of gas oil per volume of catalyst per hour and a temperature of 850 F. During this period the yield of gasoline produced from the gas oil was 26.5% by volume.

Example 4 Some of the same titania gel used in Example 3 was impregnated with sufliclent boric acid solution to incorporate therein 10% of boric oxide and was activated in the same manner. When tested for a two hour period under the same conditions used in Example 3, the yield of gasoline was 31.5%. This catalyst after operating for a two hour period was regenerated by burning with air. During the regeneration process the temperature of the catalyst reached a maximum of 1840 F. On a subsequent two hour cracking period under the same conditions, this batch of catalyst converted 34% of the gas oil to gasoline.

Ewample 5 A part of the same batch of titania gel used in the previous examples was impregnated with willcient boric acid solution to incorporate therein about 15% of boria. This catalyst when activated and tested under the same conditions described above, gave an 18.0% yield of gasoline.

Example 6 It will be understood that while my catalysts are particularly suitable for use in cracking drocarbon oils, they may be used for other purposes.

Many modifications of my invention will sugest themselves to those who are familiar with this art, audit is my intention to claim not only the express subject matter hereinbefore disclosed but also all reasonable modifications thereof except that excluded by the terms of the appended claims.

Iclaim:

1. In the method of preparing catalysts containing titania, the improvement which comprises mixing titanyl sulfate solution with ammonium hydroxide solution to form a voluminous titania jelly, the relative proportions of titanyl sulfate and ammonium hydroxide solutions being such as to impart to the supernatant liquid an excess acidity of about 0.001 to about 0.1 normal, washing the jelly until incipient peptization begins, drying the washed jelly, further washing the dried jelly to remove reaction impurities, heating the dried jelly to obtain a gel having an apparent density of between 1.00 and 1.30 grams per cubic centimeter, impregnating the gel with sufficient boric acid solution to incorporate therein 5 to 20% of boric oxide and activating the gel at a temperature of about 800 F.

2. The method set forth in claim 1 wherein the supernatant liquid has an excess acidity of about 0.001 to 0.005 normal.

3. The method set forth in claim 1 wherein the gel is impregnated with suflicient boric acid solution to incorporate therein 10% of boric oxide.

4. In the method of preparing catalysts conill taining titania, the improvement which comprises mixing titanyl sulfate solution with ammonium hydroxide solution to form a voluminous titania jelly, the relative proportions of titanyl sulfate and ammonium hydroxide solutions being such as to impart to the supernatant liquid an excess acidity of about 0.001 to about 0.1 normal, washing the jelly until incipient peptization begins, drying the washed jelly, heating the dried jelly to a temperature of 800 F.-1000 F., washing the dried jelly to remove reaction impurities, heating the dried jelly to obtain a gel having an apparent density of between 1.00 and 1.30 grams per cubic centimeter, impregnating the gel with sufiicient boric acid solution to incorporate therein 5 to 20% of boric oxide and activating the gel at a temperature of about 800 F.

GERALD C. CONNOLLY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,868,565 Connolly July 26, 1932 1,985,343 Connolly et al Dec. 25, 1934 1,996,009 Krauch et a1 Mar. 26, 1935 2,232,727 Peterkin Feb. 25, 1941 2,279,198 Huppke Apr. 7, 1942 2,339,249 Danforth Jan. 18, 1944 FOREIGN PATENTS Number Country Date 501,736 Great Britain Feb. 27, 1939 

